1. Technical Field
The embodiments described herein are related to wireless communication, and in particular to low cost, low power radio circuit implementations.
2. Related Art
All wireless communications systems use a radio to transmit and receive wireless communication signals. Radio design for wireless communication systems is well established and most such systems use similar architectures for the transmit and receive circuits; however, as wireless communication capabilities are being embedded into ever more and ever smaller devices, conventional radio circuit designs struggle to provide the low cost and low power capabilities that such devices require.
FIG. 4 is a diagram illustrating a block diagram of a conventional wireless communication circuit 100. As can be seen circuit 100 comprises a digital section 102 and a radio section 104. The radio 104 is interfaced with an antenna 106, although it will be understood that certain designs can use or require multiple antennae. The circuit 100 comprises a transmit path (tx) and a receive path (rx). For the transmit path, data signals to be communicated are generated in the digital section 102, which can be a stand-alone circuit or part of a larger digital circuit, and sent to the radio 104. The data signals are then transformed by radio 104 into signals that can be transmitted via antenna 106.
Conversely, in the receive path, signals received by antenna 106 are transformed by radio 104 into digital signals that can be processed by digital circuit 102.
FIG. 5 is a block diagram illustrating a more detailed view of the conventional radio 104; however, it will be understood that the diagram of FIG. 5 is still very high level and that many components are not illustrated. As can be seen, the transmit path comprises a Digital-to-Analog Converter (DAC) 202 configured to convert digital data signals generated by digital circuit 102 into analog signals. The analog signals can then be modulated onto a carrier signal, produced by synthesizer 218, by modulator 204. The modulated signal is then amplified by Power Amplifier (PA) 206 and transmitted via antenna 210.
In the receive path, signals received by antenna 210 are sent to Low Noise Amplifier (LNA) 212, which is configured to amplify data signals included in the signals received by antenna 210. The amplified data signals are demodulated in demodulator 214, to produce analog data signals that are then converted to digital data signals in Analog-to Digital Converter (ADC) 216 for processing by digital circuit 102.
Because the transmit and receive paths share antenna 210, a switch 208 is typically included to switch between the transmit and receive paths. Systems that use communication circuits such as circuit 100 are configured such that devices transmit and receive at certain, non-overlapping intervals, such that the devices do not transmit and receive at the same time. This is required so that the signals being transmitted do not interfere with those being received and vice versa.
Accordingly, switch 208 can be used to switch from the transmit path, during the transmission window and the receive path during the receive window, while isolating one path from the other to prevent interference. But the inclusion of the switch has some downside, especially for low power or low cost applications. Since there is a cost associated with the switch 208, its inclusion obviously drives up the overall costs of the design. But from a low power point of view, the switch 208 inherently introduces some insertion loss. Losses of this sort inherently lead to increased power, which is needed to overcome the loss. Thus, the switch 208 increases the cost and power requirements.